Fluid/foam filled seat bladder for occupant weight estimation

ABSTRACT

A seat bladder has a closed volume that is at least partially filled with an open-cell or highly-reticulated foam material. The bladder fluid soaks into interstices in the foam material and fills the remaining bladder volume. The presence of the foam material reduces the time required to evacuate the bladder prior to fluid filling, and reduces the quantity of fluid required to fill the bladder. In subsequent usage, the foam material increases the restoring force of the bladder and the dissipation of energy input to the bladder.

TECHNICAL FIELD

The present invention relates to estimating the seated weight of a seat occupant with a fluid-filled elastomeric bladder installed in the seat, and more particularly to a bladder that is at least partially filled with an open-cell foam material.

BACKGROUND OF THE INVENTION

It has been demonstrated that the weight of a vehicle seat occupant can be effectively measured for purposes of determining whether to allow or suppress deployment of supplemental inflatable restraints by measuring the pressure in a fluid-filled seat bladder. See, for example, the U.S. Pat. Nos. 5,987,370 and 6,246,936, incorporated by reference herein. Silicone is a suitable bladder fluid, because it is non-corrosive and not subject to freezing even under extreme ambient conditions. As described in the U.S. Pat. No. 6,101,436, also incorporated by reference herein, the upper and lower surfaces of the seat bladder can be joined by a pattern of spot welds in order to prevent pooling and to reduce the amount of fluid required to fill the bladder.

SUMMARY OF THE INVENTION

The present invention is directed to an improved seat bladder in which the closed volume of the bladder is at least partially filled with an open-cell or highly-reticulated foam material at the time of bladder manufacture. When fluid is subsequently added to the bladder, it soaks into interstices in the foam material and fills the remaining bladder volume. In manufacture, the presence of the foam material reduces the time required to evacuate the bladder prior to fluid filling, and reduces the quantity of fluid required to fill the bladder. In usage, the foam material increases the restoring force of the bladder and the dissipation of energy input to the bladder.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is an illustration of a prior art fluid-filled seat bladder installed in a vehicle seat;

FIGS. 2A and 2B depict the formation of a fluid-filled seat bladder according to a first embodiment of the present invention; and

FIGS. 3A and 3B depict the formation of a fluid-filled seat bladder according to a second embodiment of the present invention.

DESCRIPTION OF THE PREFERRED EMBODIMENT

Referring to the drawings, and particularly to FIG. 1, the reference numeral 10 generally designates a vehicle seat equipped with a prior art occupant weight estimation apparatus including a fluid-filled seat bladder 12. The seat 10 includes a frame and cushion pad 14, a bottom foam cushion 16 and a back foam cushion 18. A set of fasteners 19 attach the seat 10 to a pair of tracks 20 that are secured to risers, which in turn, are secured to the vehicle floor 22. A bladder assembly 24 is sandwiched between the bottom cushion 16 and the frame and cushion pad 14, and a fabric cover 26 envelops the cushion 16, bladder assembly 24 and the frame and cushion pad 14.

In the embodiment of FIG. 1, the bladder assembly 24 comprises the fluid-filled bladder 12, upper and lower interface panels 32 and 34, and a pressure sensor 40. The bladder 12 is formed of upper and lower sheets 12 a, 12 b of elastomeric material that are peripherally welded as indicated by the reference numeral 36 to form a closed volume, and selectively spot welded within the peripheral weld 36 as indicated by the reference numerals 38 to form a plurality of flow-through cells. The bladder 12 is filled with a fluid such as silicone that is non-corrosive and less subject to freezing under any naturally occurring ambient temperature conditions. In general, the weight of an occupant seated on the cushion 16 is applied to the bladder 12, and an electronic controller 42 coupled to the pressure sensor 40 develops a response to the occupant weight pressure on the bladder 12 and/or its variation with respect to time; see, for example, the aforementioned U.S. Pat. Nos. 5,987,370 and 6,246,936. As noted in the aforementioned U.S. Pat. No. 6,101,436, the inter-peripheral welds 38 can prevent pooling of fluid within bladder 12 and also reduce the amount of fluid required to fill the bladder 12.

The present invention is directed to an improved seat bladder in which the closed volume of the bladder is at least partially filled with an open-cell or highly-reticulated foam material at the time of bladder manufacture. When fluid is subsequently added to the bladder, it soaks into interstices in the foam material and fills the remaining bladder volume. The open cell foam reduces the volume of air in the sealed bladder; this reduces the time required to evacuate the bladder prior to fluid filling, and reduces the quantity of fluid required to subsequently fill the bladder. Reducing the quantity of silicone in the bladder is significant for at least two reasons: (1) it reduces the weight of the bladder, and (2) it reduces the cost of the bladder. Furthermore, the open cell foam material retains its springiness after manufacture; this increases the dissipation of energy when a load is applied to the bladder, and increases the restoring force of the bladder when the load is subsequently removed.

FIGS. 2A-2B and FIGS. 3A-3B respectively depict the formation of an open cell foam containing seat bladder 50, 60 according to first and second embodiments of this invention. In each case, a sheet 52, 52′ of open cell foam material similar in shape to that of the intended bladder 50,60, but somewhat smaller in area, is positioned between two sheets 54, 56 of elastomeric material that will become the upper and lower bladder sheets 12 a, 12 b. Preferably, both the open cell foam material 52, 52′ and the elastomeric sheets 54, 56 are made from polyurethane. A nominal thickness of the elastomeric sheets 54, 56 is 0.36 mm, and a nominal thickness of the open cell foam material 52, 52′ is 5 mm.

Marginal portions of the elastomeric sheets 54, 56 are joined together to form the peripheral seam or weld 36, sealing the sheet 52, 52′ of open cell foam material within the bladder 50, 60. Thereafter, a the upper and lower sheets 54, 56 are joined in a pattern of spot welds 38 within the peripheral weld 36, as illustrated in FIG. 1. According to the first embodiment depicted in FIGS. 2A-2B, the sheet 52 of open cell foam material is continuous within the peripheral weld 36, and is included in the spot welds 38. Such inclusion of the open cell foam material within the spot welds 38, and optionally within the peripheral weld 36 as well, is achieved most effectively when the elastomeric sheets 54, 56 and the open cell foam material 52 are both comprised of the same substance such as polyurethane. According to the second embodiment depicted in FIGS. 3A-3B, the sheet 52′ of open cell foam material is provided with openings 58 within its periphery that are aligned with the intended locations of the spot welds 38; in this case, none of the open cell foam material 52′ is included in the spot welds 38.

In summary, the present invention provides an improved seat bladder that encloses an open cell foam material. The presence of the foam material reduces the time required to evacuate the bladder prior to fluid filling, and when the fluid is added, it soaks into interstices in the foam material and fills the remaining bladder volume. The open cell foam material may have a porosity in the range about 5-20 pores per inch, and a porosity of 10 pores per inch is considered to be optimal. The reduced quantity of fluid within the bladder reduces the bladder weight, and makes the bladder assembly 24 easier to install in a seat 10. Additionally, the color of the foam material may be selected to permit easy and reliable visual distinction between versions of the bladder. And in subsequent usage, the foam material increases the restoring force of the bladder and the dissipation of energy input to the bladder, as mentioned above.

While the invention has been described with respect to the illustrated embodiment, it is recognized that numerous modifications and variations in addition to those mentioned herein will occur to those skilled in the art. For example, even though the use of period spot welds as illustrated herein is believed to provide the best overall performance in an occupant weight detection system, it may be desired to dispense with the spot welds and to use the open cell foam material to minimize distension of the bladder and consequent pooling of the bladder fluid. This can be achieved, for example, by bonding the open cell foam material to the upper and lower sheets of elastomeric material prior to the peripheral welding operation. Accordingly, it is intended that the invention not be limited to the disclosed embodiment, but that it have the full scope permitted by the language of the following claims. 

1. A seat bladder for estimating the weight of a seat occupant, comprising: upper and lower sheets of elastomeric material joined by a peripheral seam to define a closed volume; a sheet of foam material disposed between said upper and lower sheets of elastomeric material within said peripheral seam, said foam material defining a network of interconnected cells; and a fluid disposed within said closed volume and substantially filling said network of interconnected cells.
 2. (canceled)
 3. The seat bladder of claim 1, further comprising: at least one weld joining said upper and lower sheets of elastomeric material within said peripheral seam, said sheet of open cell foam material having an opening aligned with said weld so that said open cell foam material is not included in said weld.
 4. The seat bladder of claim 1, further comprising: at least one weld joining said upper and lower sheets of elastomeric material within said peripheral seam, where said weld includes a region of open cell foam material intermediate the joined upper and lower sheets of elastomeric material.
 5. The seat bladder of claim 4, wherein said elastomeric material and said open cell foam material both comprise polyurethane.
 6. The seat bladder of claim 1, wherein said open cell foam material has a porosity in the range of about five pores per inch to about twenty pores per inch.
 7. The seat bladder of claim 1, wherein said fluid comprises silicone. 